igneous
Basalt Pebble
Basalt
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. This specimen appears to be water-worn, indicating it was shaped by river or coastal erosion.
Uses & applications
Commonly used in construction as aggregate for concrete and asphalt, as railroad ballast, and occasionally for stonework or landscaping.
Geological facts
Basalt is the most common volcanic rock on Earth and also makes up most of the ocean floor. It is found on the Moon and Mars as well.
Field identification & locations
Identified by its dark color, heavy weight for its size, and very fine-grained texture. Commonly found in former volcanic regions and along shorelines.
